Advances in field noble gasmeasurements towards operationalhydrology

Abstract

International audienceIn natural waters, noble gas concentrations are governedby a diversity of relatively simple and well-studied physicalprocesses. As a result, noble gas measurements provideimportant information on various phenomena such asgroundwater residence time distribution (4He, 21Ne, 37Ar, 39Ar,40Ar, 85Kr, 81Kr), aquifer recharge conditions (temperature,elevation …) or aquifer-river exchange (222Rn).However, despite their interest, noble gas data remainrelatively scarce and punctual owing to the complexity andcosts of their production. In view of the spatial and temporalvariety and variability of the Hydrosphere dynamics a newinvestigation method is needed.This study approaches the concept of “operationalhydrology” aiming to enhance both the spatio-temporaldistribution and the quality of environmental data for athorough exploration of the Hydrosphere.In this perspective, we developed a new analytical toolbased on membrane inlet mass spectrometry (MIMS)allowing the continuous measurement of dissolved gases(Chatton et al., 2017).To illustrate our approach, we present atmospheric andradiogenic noble gas data (He, Ne, Ar, Kr, Xe) measured insitu with a CF-MIMS (Chatton et al, 2017) installed in amobile laboratory arranged in an all-terrain truck (CRITEXLab).This ongoing work focuses on groundwater and thefield investigation of residence time distribution, rechargeprocesses, water flow paths and mixing